CN113366123A - Method for producing grain-oriented electromagnetic steel sheet - Google Patents

Method for producing grain-oriented electromagnetic steel sheet Download PDF

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Publication number
CN113366123A
CN113366123A CN202080008981.8A CN202080008981A CN113366123A CN 113366123 A CN113366123 A CN 113366123A CN 202080008981 A CN202080008981 A CN 202080008981A CN 113366123 A CN113366123 A CN 113366123A
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China
Prior art keywords
steel sheet
base steel
insulating film
intermediate layer
grain
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CN202080008981.8A
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Chinese (zh)
Inventor
新井聪
牛神义行
滨村秀行
山本信次
奥村俊介
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Nippon Steel Corp
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Nippon Steel and Sumitomo Metal Corp
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Publication of CN113366123A publication Critical patent/CN113366123A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K15/00—Electron-beam welding or cutting
    • B23K15/0046—Welding
    • B23K15/0086—Welding welding for purposes other than joining, e.g. built-up welding
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    • B23K15/00—Electron-beam welding or cutting
    • B23K15/0046—Welding
    • B23K15/0093—Welding characterised by the properties of the materials to be welded
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    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
    • B23K26/355—Texturing
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1222—Hot rolling
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C21D8/1216—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties the working step(s) being of interest
    • C21D8/1233—Cold rolling
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    • C21—METALLURGY OF IRON
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    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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    • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
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    • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
    • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
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    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
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    • B23K2101/00—Articles made by soldering, welding or cutting
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    • B23K2103/02—Iron or ferrous alloys
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Abstract

The method for producing a grain-oriented electrical steel sheet according to the present invention is characterized by comprising: a deformation region forming step of irradiating an electron beam to a grain-oriented electrical steel sheet having a base steel sheet (1), an intermediate layer (4) disposed in contact with the base steel sheet (1), and an insulating film (3) disposed in contact with the intermediate layer (4), thereby forming a deformation region (D) extending in a direction intersecting with a rolling direction of the base steel sheet (1) on a surface of the base steel sheet (1), wherein in the deformation region forming step, a central portion of the deformation region (D) in the rolling direction of the base steel sheet (1) and the extending direction of the deformation region (D) is heated to 800 to 2000 ℃.

Description

Method for producing grain-oriented electromagnetic steel sheet
Technical Field
The present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent coating adhesion. In particular, the present invention relates to a method for producing a grain-oriented electrical steel sheet having excellent adhesion even without a forsterite film or an insulating film.
The present application claims priority based on japanese patent application No. 2019-005059, filed in japan on day 16/1/2019, the contents of which are incorporated herein by reference.
Background
Grain-oriented electrical steel sheets are soft magnetic materials and are mainly used as iron core materials of transformers. Therefore, high magnetization characteristics and low core loss magnetic characteristics are required. The magnetization characteristic refers to a magnetic flux density excited when the iron core is excited. The higher the magnetic flux density, the more the core can be made smaller, which is advantageous in terms of the device configuration of the transformer and also advantageous in terms of the manufacturing cost of the transformer.
In order to improve the magnetization characteristics, it is necessary to control the grain texture so as to form as many crystal grains as possible, in which the {110} plane is aligned parallel to the steel sheet surface and the <100> axis is aligned in the rolling direction, and in which the crystal orientation (gaussian orientation) is aligned. In order to concentrate the crystal orientation in a gaussian orientation, an inhibitor such as AlN, MnS, MnSe, or the like is usually finely precipitated in steel to control secondary recrystallization.
The iron loss is power loss consumed as heat energy when the iron core is excited by the ac magnetic field. From the viewpoint of energy saving, it is required that the iron loss be as low as possible. The degree of iron loss is influenced by magnetic susceptibility, sheet thickness, film tension, impurity amount, resistivity, crystal grain size, magnetic domain size, and the like. Even at present, various technologies have been developed for electrical steel sheets, and research and development for reducing iron loss has been continued in order to improve energy efficiency.
Another characteristic required for grain-oriented electrical steel sheets is a characteristic of a coating film formed on the surface of a base steel sheet. In general, in grain-oriented electrical steel sheet, as shown in fig. 1, Mg is formed on base steel sheet 12SiO4 A forsterite film 2 mainly composed of (forsterite), and an insulating film 3 is formed on the forsterite film 2. The forsterite film and the insulating film have a function of electrically insulating the surface of the base steel sheet and applying tension to the base steel sheet to reduce the iron loss. In addition, the forsterite film contains Mg in addition to Mg2SiO4In addition, the steel sheet may contain a small amount of impurities or additives contained in the base steel sheet or the annealing separator, and reaction products thereof.
The insulating film is not peeled from the electromagnetic steel sheet in order to exhibit insulation properties or a required tension. Therefore, the insulating film is required to have high film adhesion. However, it is difficult to simultaneously improve both the tension applied to the base steel sheet and the film adhesion. Now, research and development to improve both of them is continuously ongoing.
Grain-oriented electrical steel sheets are generally produced in the following order. A silicon steel billet containing 2.0 to 7.0 mass% of Si is hot-rolled, the hot-rolled steel sheet is annealed as required, and then the annealed steel sheet is cold-rolled 1 time or more with intermediate annealing interposed therebetween to be processed into a steel sheet having a final thickness. Thereafter, decarburization annealing is performed on the steel sheet having the final thickness in a wet hydrogen atmosphere, and in addition to decarburization, primary recrystallization is promoted and an oxide layer is formed on the surface of the steel sheet.
An annealing separator containing MgO (magnesium oxide) as a main component is applied to a steel sheet having an oxide layer, dried, and then wound into a coil shape. Then, the coil-shaped steel sheet is subjected to final annealingThe secondary recrystallization is promoted to concentrate the crystal orientation of the crystal grains in the gaussian orientation. Further, MgO in the annealing separating agent and SiO in the oxide layer are caused to react2(silica) reaction to form Mg on the surface of the base steel sheet2SiO4An inorganic forsterite film as a main component.
Next, the steel sheet having the forsterite film is subjected to purification annealing to remove the impurities in the base steel sheet by diffusing them outward. After the steel sheet is subjected to the flattening annealing, a solution mainly containing phosphate and colloidal silica is applied to the surface of the steel sheet having the forsterite film, for example, and the resultant is sintered to form an insulating film. In this case, a tensile force due to a difference in thermal expansion coefficient is applied between the base steel sheet, which is crystalline, and the substantially amorphous insulating film. Therefore, the insulating film is also sometimes referred to as a tension film.
With Mg2SiO4The interface between the forsterite film (fig. 1, 2) and the steel sheet (fig. 1, 1) is usually uneven (see fig. 1). The uneven interface slightly reduces the effect of reducing the iron loss due to the tension. Since the iron loss is reduced by smoothing the interface, the following development has been carried out.
Patent document 1 discloses a production method in which a forsterite film is removed by means of pickling or the like, and the surface of a steel sheet is smoothed by chemical polishing or electrolytic polishing. However, in the manufacturing method of patent document 1, the insulating film may be difficult to adhere to the surface of the base steel sheet.
Therefore, in order to improve the adhesion of the insulating film to the film processed to a smooth steel sheet surface, as shown in fig. 2, it is proposed to form an intermediate layer 4 (or an underlying film) between the base steel sheet and the insulating film. The base film formed by coating an aqueous solution of a phosphate or an alkali metal silicate disclosed in patent document 2 also has an effect on the film adhesion. As a further effective method, patent document 3 discloses a method of annealing a steel sheet in a specific atmosphere before forming an insulating film to form an external oxidation type silica layer as an intermediate layer on the surface of the steel sheet.
By forming such an intermediate layer, the film adhesion can be improved, but since a large facility such as an electrolytic treatment facility or a dry coating facility is newly required, it is difficult to secure a land and the production cost may be increased.
Patent documents 4 to 6 disclose that when an insulating film containing an acidic organic resin substantially not containing chromium as a main component is formed on a steel sheet, a phosphorus compound layer (FePO) is formed between the steel sheet and the insulating film4、Fe3(PO4)2、FeHPO4、Fe(H2PO4)2、Zn2Fe(PO4)2、Zn3(PO4)2And a layer formed of a hydrate of the above or a layer formed of a phosphate of Mg, Ca or Al, and having a thickness of 10 to 200nm), and improving the appearance and adhesion of the insulating film.
On the other hand, as a method for reducing abnormal eddy current loss, which is one of the iron losses, there is known a magnetic domain control method in which stress deformation portions or groove portions extending in a direction perpendicular to the rolling direction are formed at predetermined intervals along the rolling direction, thereby narrowing the width of 180 ° magnetic domains (performing subdivision of 180 ° magnetic domains). In the method of forming stress deformation, the 180 ° domain-segmentation effect of the reflow domain generated in the deformed portion (deformed region) is utilized. A typical method thereof is a method using shock waves or rapid heating by laser beam irradiation. In this method, the stress-deformed portion is formed in the base steel sheet with almost no change in the surface shape of the irradiated portion. In addition, the method of forming the grooves utilizes the effect of a diamagnetic field generated by magnetic poles generated on the side walls of the grooves. That is, the domain control is classified into a deformation imparting type and a groove forming type.
For example, patent document 7 discloses that after oxides on the surface of a steel sheet that has been finally annealed are removed to form a smooth surface, a coating film is formed on the surface, and magnetic domains are subdivided by irradiation with a laser beam, an electron beam, or a plasma flame.
Documents of the prior art
Patent document
Patent document 1 Japanese patent laid-open publication No. S49-096920
Patent document 2 Japanese patent application laid-open No. H05-279747
Patent document 3, Japanese patent application laid-open No. H06-184762
Patent document 4 Japanese patent laid-open No. 2001-220683
Patent document 5, Japanese patent laid-open No. 2003-193251
Patent document 6, Japanese patent laid-open No. 2003-193252
Patent document 7 Japanese patent application laid-open No. 11-012755
Disclosure of Invention
Technical problem to be solved by the invention
The grain-oriented electrical steel sheet having a three-layer structure of "base steel sheet-silicon oxide main body intermediate layer-insulating coating film" and having no forsterite coating film of the above example has a problem that the magnetic domain width is wider than that of the grain-oriented electrical steel sheet having a forsterite coating film shown in fig. 1. The present inventors have studied various magnetic domain controls on grain-oriented electrical steel sheets having no forsterite film, and as a result, have found that it is preferable to subdivide the magnetic domains when increasing the energy density of a laser beam or an electron beam irradiated to the grain-oriented electrical steel sheets.
However, according to the studies of the present inventors, it has been found that increasing the energy density of a laser beam or an electron beam promotes the subdivision of magnetic domains and affects the insulating film. Specifically, when a laser beam or an electron beam having a high energy density is irradiated, a problem is found in that the structure of the insulating film is changed by the influence of irradiation heat, and the adhesiveness of the insulating film is lowered.
The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a grain-oriented electrical steel sheet, which is free of a forsterite film and in which a deformed region is formed on a base steel sheet, and which can ensure good adhesion of an insulating film and obtain a good iron loss reduction effect.
Means for solving the problems
(1) A method for producing a grain-oriented electrical steel sheet according to an aspect of the present invention includes: and a deformed region forming step of irradiating an electron beam to a grain-oriented electrical steel sheet having a base steel sheet, an intermediate layer disposed in contact with the base steel sheet, and an insulating film disposed in contact with the intermediate layer, thereby forming a deformed region extending in a direction intersecting a rolling direction of the base steel sheet on a surface of the base steel sheet, wherein in the deformed region forming step, a central portion of the deformed region in the rolling direction of the base steel sheet and in the extending direction of the deformed region is heated to 800 ℃ to 2000 ℃.
(2) The method for producing a grain-oriented electrical steel sheet according to the above (1), wherein in the deformed region forming step, the temperature of the central portion of the deformed region in the rolling direction of the base steel sheet and the extending direction of the deformed region may be heated to 800 to 1500 ℃.
(3) The method of producing a grain-oriented electrical steel sheet according to the above (1) or (2), wherein in the deformed region forming step, the irradiation conditions of the electron beam may be an acceleration voltage: 50 kV-350 kV, beam current: 0.3 mA-50 mA, electron beam irradiation diameter: 10 μm to 500 μm, irradiation interval: 3 mm-20 mm, scanning speed: 5 m/s to 80 m/s.
(4) The method of producing a grain-oriented electrical steel sheet according to any one of the above (1) to (3), further comprising an intermediate layer forming step of forming an intermediate layer on the base steel sheet, wherein in the intermediate layer forming step, the annealing temperature may be adjusted to: 500-1500 ℃, holding time: 10-600 seconds, dew point: heat-treating the base steel sheet under annealing conditions at-20 to 5 ℃ to form an intermediate layer.
(5) The method of producing a grain-oriented electrical steel sheet according to any one of the above (1) to (4), further comprising an insulating film forming step of forming an insulating film on the base steel sheet having the intermediate layer formed thereon, wherein the insulating film forming step is performed at a coating amount of 2g/m2～10g/m2Coating the surface of a base steel sheet with an insulating film-forming solution, and leaving the base steel sheet coated with the insulating film-forming solution for 3 to 300 seconds in a state of containing hydrogen and nitrogen and having an oxidation degree PH2O/PH2Adjusting the temperature to 0.001-0.3 in atmosphere gas, and coating at a heating rate of 5-30 ℃/sHeating a base steel plate coated with an insulating film-forming solution at an oxidation degree PH containing hydrogen and nitrogen2O/PH2Soaking the heated base steel plate in an atmosphere gas adjusted to 0.001 to 0.3 at a temperature of 300 to 950 ℃ for 10 to 300 seconds to a degree of oxidation PH containing hydrogen and nitrogen2O/PH2And cooling the soaked base material steel plate to 500 ℃ at a cooling speed of 5-50 ℃/s in an atmosphere gas controlled to be 0.001-0.05 ℃.
Effects of the invention
According to the present invention, there can be provided a method for producing a grain-oriented electrical steel sheet, in which a forsterite film is not formed and a deformed region is formed on a base steel sheet, and a good adhesion of the insulating film can be ensured, thereby obtaining a good iron loss reduction effect.
Drawings
Fig. 1 is a schematic cross-sectional view showing a film structure of a conventional grain-oriented electrical steel sheet.
Fig. 2 is a schematic cross-sectional view showing another film structure of a conventional grain-oriented electrical steel sheet.
Fig. 3 is a schematic cross-sectional view for explaining a deformed region obtained by the method for producing a grain-oriented electrical steel sheet according to one embodiment of the present invention.
Fig. 4 is a schematic cross-sectional view of an enlarged portion a of fig. 3.
Fig. 5 is a diagram for explaining definition of line segment fractions of voids in a grain-oriented electrical steel sheet according to the same embodiment.
Detailed Description
The present inventors have found that a difference occurs in the adhesion of the insulating film between when a grain-oriented electrical steel sheet having no forsterite film is irradiated with a laser beam and when an electron beam is irradiated, and have studied magnetic domain control by an electron beam.
The present inventors have intensively studied grain-oriented electrical steel sheets without forsterite film and changed irradiation conditions of electron beams, and as a result, they have found that the width of magnetic domains can be narrowed and the adhesion of the insulating film can be secured under specific irradiation conditions.
The present inventors have also found that when the above-described specific irradiation conditions are not satisfied, voids are generated in the insulating film and the adhesion of the insulating film deteriorates even if the width of the magnetic domain is controlled to be narrow.
Further, the present inventors have found that, although the insulating film after irradiation does not change under the conventional irradiation conditions, when a deformed region is formed under the above-mentioned specific irradiation conditions, it is observed that M is included in the central portion and the vicinity thereof2P4O13The characteristic structure of (1).
Preferred embodiments of the present invention will be described below. However, the present invention is not limited to the configurations disclosed in the embodiments, and various modifications can be made without departing from the scope of the present invention. It is needless to say that the elements of the following embodiments may be combined with each other within the scope of the present invention.
In the following embodiments, the numerical limitation range indicated by the term "to" means a range including the numerical values recited before and after the term "to" as the lower limit value and the upper limit value. Numerical values expressed as "greater than" or "less than" do not include the value within the numerical range.
[ method for producing grain-oriented Electrical Steel sheet ]
The method for producing a grain-oriented electrical steel sheet according to the present invention will be described below. The method for producing a grain-oriented electrical steel sheet according to the present embodiment is not limited to the following method. The following manufacturing method is an example of a method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment.
The grain-oriented electrical steel sheet of the present embodiment may be produced by: in the final annealing, the formation of a forsterite film is suppressed, or after the final annealing, an intermediate layer is formed, an insulating film is formed, and a deformed region is formed on a base steel sheet from which the forsterite film has been removed.
The method for manufacturing a grain-oriented electrical steel sheet according to the present embodiment includes the steps of: and a deformation region forming step of irradiating an electron beam to a grain-oriented electrical steel sheet having a base steel sheet, an intermediate layer disposed in contact with the base steel sheet, and an insulating film disposed in contact with the intermediate layer, and forming a deformation region extending in a direction intersecting the rolling direction on the surface of the base steel sheet.
In the deformed region forming step of the method for producing a grain-oriented electrical steel sheet according to the present embodiment, the temperature of the center portion of the deformed region in the rolling direction and the extending direction of the deformed region is heated to 800 to 2000 ℃.
In the method for producing a grain-oriented electrical steel sheet according to the present embodiment,
(a) annealing the base steel sheet from which a coating film of an inorganic mineral such as forsterite formed in the final annealing is removed by pickling, grinding, or the like;
or (b) annealing the base steel sheet in which the formation of the film of the inorganic mineral is suppressed in the final annealing;
(c) forming an intermediate layer on the surface of the base steel sheet by thermal oxidation annealing, that is, annealing in an atmosphere in which the dew point is controlled;
(d) the intermediate layer is coated with a solution for forming an insulating film mainly composed of phosphate and colloidal silica, and sintered.
By the above-described manufacturing method, a grain-oriented electrical steel sheet having a base steel sheet, an intermediate layer disposed in contact with the base steel sheet, and an insulating film disposed in contact with the intermediate layer and serving as the outermost surface can be manufactured.
The base steel sheet is produced, for example, as follows.
A silicon steel slab containing 0.8 to 7.0 mass% of Si, preferably a silicon steel slab containing 2.0 to 7.0 mass% of Si, is hot-rolled, the hot-rolled steel sheet is annealed as necessary, and then the annealed steel sheet is cold-rolled 1 time or 2 times or more with intermediate annealing interposed therebetween to be processed into a steel sheet having a final thickness. Next, decarburization annealing is performed on the steel sheet having the final thickness, and in addition to decarburization, primary recrystallization is promoted and an oxide layer is formed on the surface of the steel sheet.
Then, an annealing separator containing magnesium oxide as a main component is applied to the surface of the steel sheet having the oxide layer, and the steel sheet is dried and wound into a coilThe shape of the material. Subsequently, the coil-shaped steel sheet is subjected to final annealing (secondary recrystallization). Forming forsterite (Mg) on the surface of the steel sheet by final annealing2SiO4) Forsterite film as main component. The forsterite film is removed by pickling, grinding, or the like. After the removal, the surface of the steel sheet is preferably processed to be smooth by chemical polishing or electrolytic polishing.
On the other hand, as the above-mentioned annealing separator, an annealing separator containing alumina as a main component may be used instead of magnesia. An annealing separator containing alumina as a main component is applied to the surface of a steel sheet having an oxide layer, and the steel sheet is dried and wound into a coil shape. Subsequently, the coil-shaped steel sheet is subjected to final annealing (secondary recrystallization). When an annealing separating agent containing alumina as a main component is used, the formation of a coating film of an inorganic mineral such as forsterite on the surface of a steel sheet is suppressed even when final annealing is performed. After the final annealing, the surface of the steel sheet is preferably finished to be smooth by chemical polishing or electrolytic polishing.
The base steel sheet from which the film of an inorganic mineral such as forsterite has been removed or the base steel sheet from which the generation of the film of an inorganic mineral such as forsterite has been suppressed is subjected to thermal oxidation annealing under the following annealing conditions, thereby forming an intermediate layer on the surface of the base steel sheet. In addition, in some cases, the base steel sheet may be annealed without being subjected to annealing after the final annealing, and an insulating film may be formed on the surface of the base steel sheet after the final annealing.
The annealing atmosphere in the intermediate layer formation is preferably a reducing atmosphere, and particularly preferably a nitrogen atmosphere containing hydrogen mixed therein, so that the inside of the steel sheet is not oxidized. For example, hydrogen: the content of nitrogen is 80-20%: 20 to 80% (total 100%) of an atmosphere.
Further, in the formation of the intermediate layer, it is preferable that the annealing conditions are adjusted to an annealing temperature of 500 to 1500 ℃, a holding time of 10 to 600 seconds, and a dew point of-20 to 10 ℃. More preferably, the dew point is 5 ℃ or lower. By heat-treating the base steel sheet under such annealing conditions, an intermediate layer is formed on the surface of the base steel sheet.
The thickness of the intermediate layer is controlled by appropriately adjusting one or more of the annealing temperature, the holding time, and the dew point of the annealing atmosphere. The thickness of the intermediate layer is preferably 2nm to 400nm on average in order to ensure the film adhesion of the insulating film. More preferably 5nm to 300 nm.
Next, an insulating film is formed on the intermediate layer. A preferred method for forming the insulating film is as follows. The method of forming the insulating film is not limited to the following method. First, an insulating film-forming solution mainly containing phosphate and colloidal silica is applied and sintered.
Then, on the surface of the base steel sheet, the coating amount was 2g/m2～10g/m2The base steel sheet coated with the insulating film-forming solution is left for 3 to 300 seconds.
Then, in the presence of hydrogen and nitrogen at a degree of oxidation PH2O/PH2Heating the base steel sheet coated with the insulating film-forming solution at a temperature increase rate of 5 ℃/sec to 30 ℃/sec in an atmosphere gas adjusted to 0.001 to 0.3. At a hydrogen and nitrogen containing oxidation degree PH2O/PH2The base steel sheet heated under these conditions is soaked in an atmosphere gas adjusted to 0.001 to 0.3 at a temperature of 300 to 950 ℃ for 10 to 300 seconds.
At a hydrogen and nitrogen containing oxidation degree PH2O/PH2The base material steel sheet soaked under the conditions is cooled to 500 ℃ at a cooling rate of 5 ℃/second to 50 ℃/second in an atmosphere gas controlled to be 0.001 to 0.05 ℃.
When the oxidation degree of the heating-cooling atmosphere is less than the lower limit value, the intermediate layer may be thinned. If the amount exceeds the upper limit, the intermediate layer may become thick.
When the cooling rate during cooling is less than 5 ℃/sec, the productivity may be lowered. When the cooling rate exceeds 50 ℃/sec, many voids may be formed in the insulating film.
Next, the grain-oriented electrical steel sheet obtained in the above step is irradiated with an electron beam, and a deformed region extending in a direction intersecting the rolling direction is formed on the surface of the base steel sheet. Here, the center of the deformed region in the rolling direction and the extending direction of the deformed region is heated to 800 to 2000 ℃. Thereby, a deformed region extending in a direction intersecting the rolling direction is formed on the surface of the base steel sheet. Here, the center of the deformed region in the rolling direction includes the center of the deformed region (more specifically, the center between the ends of the deformed region in the rolling direction when the deformed region is viewed in cross section parallel to the rolling direction and the plate thickness direction) and has a width of 10 μm in the rolling direction. The center of the deformed region in the extending direction of the deformed region is a continuous deformed region, and is a region including a midpoint (i.e., the center) of a line segment connecting the end in the extending direction of the deformed region and the end, and is a region having a width of 10 μm in the extending direction of the deformed region from the midpoint (center).
Therefore, the region corresponding to both the central portion of the deformed region in the rolling direction and the central portion of the deformed region in the extending direction of the deformed region is heated to 800 to 2000 ℃.
Here, in order to heat the temperature of the central portion of the deformed region in the rolling direction and the extending direction of the deformed region to 800 to 2000 ℃, in the deformed region forming step, it is preferable to set the acceleration voltage: 50 kV-350 kV, beam current: 0.3 mA-50 mA, electron beam irradiation diameter: 10 μm to 500 μm, irradiation interval: 3 mm-20 mm, scanning speed: irradiating an electron beam at a rate of 5 m/sec to 80 m/sec. The electron beam is preferably used because it has a characteristic such as an effect of suppressing skin damage due to an increase in acceleration voltage and the ability to control the electron beam at high speed.
In the deformed region forming step, the temperature of the central portion of the deformed region in the rolling direction and the extending direction of the deformed region may be heated to 800 to 1500 ℃.
The irradiation with the electron beam is preferably performed by scanning the electron beam from one width end of the steel sheet to the other width end using 1 or 2 or more irradiation devices (e.g., electron guns). The scanning direction of the electron beam is preferably an angle of 45 to 135 ° in the clockwise direction or the counterclockwise direction with respect to the rolling direction, parallel to the surface of the grain-oriented electrical steel sheet, and more preferably 90 °, that is, a direction parallel to and perpendicular to the surface of the grain-oriented electrical steel sheet with respect to the rolling direction. When the deviation from the distance of 90 ° increases, the volume of the deformation region becomes too large, and hysteresis loss tends to increase.
The acceleration voltage is preferably 50kV to 350 kV.
The acceleration voltage of the electron beam is preferably high. The higher the acceleration voltage of the electron beam, the higher the substance permeability of the electron beam, and the more likely the electron beam passes through the insulating film. Thus, damage to the insulating film is suppressed. In addition, when the acceleration voltage is high, there is an advantage that the electron beam diameter is easily reduced. In order to obtain the above effects, the acceleration voltage is preferably 50kV or more. The acceleration voltage is preferably 70kV or more, and more preferably 100kV or more.
On the other hand, the acceleration voltage is preferably 350kV or less from the viewpoint of suppressing the facility cost. The acceleration voltage is preferably 300kV or less, more preferably 250kV or less.
The beam current is preferably 0.3mA to 50 mA.
The beam current is preferably small from the viewpoint of reducing the beam diameter. Since an excessively large beam current may make it difficult to collect and bundle the electron beams, it is preferable to set the beam current to 50mA or less. Further, the beam current is more preferably 30mA or less. If the beam current is too small, the deformation necessary to obtain a sufficient magnetic domain refinement effect may not be formed, and therefore, the beam current is preferably set to 0.3mA or more. The beam current is more preferably 0.5mA or more, and still more preferably 1mA or more.
The electron beam irradiation diameter is preferably 10 μm to 500. mu.m.
The smaller the electron beam irradiation diameter in the direction perpendicular to the scanning direction of the electron beam, the more advantageous the improvement of the single-plate iron loss. The irradiation diameter of the electron beam in the direction perpendicular to the scanning direction of the electron beam is preferably 500 μm or less. In the present embodiment, the electron beam irradiation diameter is defined as the half-width of the beam profile measured by the slit method (using a slit having a width of 0.03 mm). The electron beam irradiation diameter in the direction perpendicular to the scanning direction is preferably 400 μm or less, and more preferably 300 μm or less.
The lower limit of the electron beam irradiation diameter in the direction perpendicular to the scanning direction is not particularly limited, and is preferably 10 μm or more. When the irradiation diameter of the electron beam in the direction perpendicular to the scanning direction of the electron beam is 10 μm or more, a wide range can be irradiated with 1 electron beam source. The electron beam irradiation diameter in the direction perpendicular to the scanning direction is preferably 30 μm or more, and more preferably 100 μm or more.
The irradiation interval is preferably 3mm to 20 mm.
Further, by setting the irradiation interval to 3mm to 20mm, the effect of reducing the iron loss due to the balance between the eddy current loss reduction by the domain subdivision and the suppression of the increase in the hysteresis loss can be obtained. The irradiation interval is a distance along the rolling direction of the base steel sheet to which the electron beam is irradiated, and is an interval of the deformed region in the rolling direction.
The scanning speed is preferably 5 m/sec to 80 m/sec.
Further, the scanning speed is 5 m/sec to 80 m/sec, whereby both the magnetic domain refining effect and productivity can be achieved.
The scanning speed of the electron beam is preferably 5 m/sec or more. Here, the scanning speed refers to a scanning speed obtained by dividing a distance from an irradiation start point to an irradiation end point of the electron beam when each of the deformation regions is formed by a time required for scanning between the points, that is, an average scanning speed. For example, when the irradiation start point and the irradiation end point of the electron beam are both ends in the width direction of the steel sheet, the scanning speed is an average scanning speed (speed obtained by dividing the distance between the width ends of the steel sheet by the time required for scanning between the width ends) during the period in which the irradiation is performed while scanning the electron beam from the width end to the other width end of the steel sheet. When the scanning speed is less than 5 m/sec, the processing time may be increased, and productivity may be lowered. The scanning speed is more preferably 45 m/sec or more.
Next, an example of a grain-oriented electrical steel sheet obtained by the method for producing a grain-oriented electrical steel sheet according to the above embodiment will be described. However, it goes without saying that the grain-oriented electrical steel sheet obtained by the method for producing a grain-oriented electrical steel sheet according to the present invention is not limited to the following embodiments.
[ grain-oriented Electrical Steel sheet ]
The grain-oriented electrical steel sheet of the present embodiment includes a base steel sheet, an intermediate layer disposed in contact with the base steel sheet, and an insulating film disposed in contact with the intermediate layer.
The grain-oriented electrical steel sheet of the present embodiment has a deformed region extending in a direction intersecting the rolling direction on the surface of the base steel sheet, and M is present in the insulating film on the deformed region in a cross-sectional view of a plane parallel to the rolling direction and the sheet thickness direction2P4O13. M is at least one of Fe or Cr or both.
The grain-oriented electrical steel sheet of the present embodiment includes a base steel sheet, an intermediate layer disposed in contact with the base steel sheet, and an insulating film disposed in contact with the intermediate layer, and does not include a forsterite film.
Here, the grain-oriented electrical steel sheet having no forsterite coating film refers to a grain-oriented electrical steel sheet produced by removing a forsterite coating film after production, or a grain-oriented electrical steel sheet produced by suppressing the formation of a forsterite coating film.
In the present embodiment, the rolling direction of the base steel sheet is the rolling direction in hot rolling or cold rolling in producing the base steel sheet by the production method described later. The rolling direction may be referred to as a direction of passing the steel sheet, a direction of conveyance, or the like. The rolling direction is the longitudinal direction of the base steel sheet. The rolling direction can be specified by using a device for observing a magnetic domain structure or a device for measuring crystal orientation such as an X-ray Laue method.
In the present embodiment, the direction intersecting the rolling direction is a direction extending from a direction parallel to and perpendicular to the surface of the base steel sheet with respect to the rolling direction (hereinafter, simply referred to as "direction perpendicular to the rolling direction") to a direction parallel to the surface of the base steel sheet within an inclination range of 45 ° clockwise or counterclockwise. Since the deformed region is formed on the surface of the base steel sheet, the deformed region extends in a direction inclined at an angle of 45 ° or less in the sheet surface of the base steel sheet from a direction perpendicular to the rolling direction and the sheet thickness direction on the surface of the base steel sheet.
The surface parallel to the rolling direction and the thickness direction means a surface parallel to both the rolling direction and the thickness direction of the base steel sheet.
The insulating film on the deformation region means a portion of the insulating film disposed on the base steel sheet, which is located at the upper portion in the thickness direction of the deformation region in a cross-sectional view of a plane parallel to the rolling direction and the thickness direction.
The following describes each constituent element of the grain-oriented electrical steel sheet of the present embodiment. The grain-oriented electrical steel sheet according to the present embodiment can be produced by the above-described method for producing a grain-oriented electrical steel sheet.
(base steel plate)
The base steel sheet as a base material has a crystal grain texture in which the crystal orientation is controlled to be gaussian in the surface of the base steel sheet. The surface roughness of the base steel sheet is not particularly limited, but is preferably 0.5 μm or less, more preferably 0.3 μm or less in terms of arithmetic average roughness (Ra) in order to impart a large tensile force to the base steel sheet and reduce the iron loss. The lower limit of the arithmetic average roughness (Ra) of the base steel sheet is not particularly limited, and when it is 0.1 μm or less, the iron loss improvement effect is saturated, so that the lower limit may be 0.1 μm.
The thickness of the base steel sheet is not particularly limited, and is preferably 0.35mm or less, more preferably 0.30mm or less on average, in order to further reduce the iron loss. The lower limit of the thickness of the base steel sheet is not particularly limited, and may be 0.10mm from the viewpoint of production facilities and cost. The method for measuring the thickness of the base steel sheet is not particularly limited, and for example, the thickness can be measured using a micrometer or the like.
The chemical composition of the base steel sheet is not particularly limited, and for example, Si is preferably contained at a high concentration (for example, 0.8 to 7.0 mass%). In this case, strong chemical affinity with the intermediate layer of the silicon oxide body is exhibited, and the intermediate layer is firmly adhered to the base steel sheet.
(intermediate layer)
The intermediate layer is disposed in contact with the base steel sheet (i.e., formed on the surface of the base steel sheet), and has a function of bonding the base steel sheet to the insulating film. The intermediate layer continuously spreads over the surface of the base steel sheet. By forming the intermediate layer between the base steel sheet and the insulating film, the adhesion between the base steel sheet and the insulating film is improved, and stress is applied to the base steel sheet.
The intermediate layer may be formed by heat-treating a base steel sheet in which the formation of a forsterite film is suppressed at the time of final annealing or a base steel sheet from which the forsterite film is removed after the final annealing in an atmosphere gas adjusted to a desired oxidation degree.
The silicon oxide to be the main body of the intermediate layer is preferably SiOx(x is 1.0 to 2.0). If the silicon oxide is SiOx(x is 1.5 to 2.0), and silicon oxide is more stable, and thus is more preferable. When the intermediate layer is formed on the surface of the base steel sheet, if the thermal oxidation annealing is sufficiently performed (that is, the conditions of the above embodiment are satisfied), SiO may be formed on the intermediate layerx(x≈2.0)。
When thermal oxidation annealing is performed under the conditions of the above embodiment, silicon oxide is amorphous as it is. Therefore, the intermediate layer made of a dense material having high strength against thermal stress, increased elasticity, and capable of easily relaxing thermal stress can be formed on the surface of the base steel sheet.
Since the intermediate layer may have a small thickness and the thermal stress relaxation effect may not be sufficiently exhibited, the thickness of the intermediate layer is preferably 2nm or more on average. The thickness of the intermediate layer is more preferably 5nm or more. On the other hand, if the thickness of the intermediate layer is large, the thickness may become uneven, and defects such as voids and cracks may occur in the intermediate layer. Therefore, the thickness of the intermediate layer is preferably 400nm or less, more preferably 300nm or less on average. The method for measuring the thickness of the intermediate layer will be described later.
The intermediate layer may also be an external oxide film formed by external oxidation. The external oxide film is an oxide film formed in a low-oxidizing atmosphere gas, and an alloying element (Si) in the steel sheet diffuses into the surface of the steel sheet, and then forms a film-like oxide on the surface of the steel sheet.
The intermediate layer contains silicon dioxide (silicon oxide) as a main component, as described above. The intermediate layer may contain an oxide of an alloying element contained in the base steel sheet in addition to silicon oxide. That is, there may be a case where the oxide or the composite oxide contains any one of Fe, Mn, Cr, Cu, Sn, Sb, Ni, V, Nb, Mo, Ti, Bi, and Al. The intermediate layer may contain metal particles such as Fe. In addition, the intermediate layer may contain impurities within a range not to impair the effects.
In the grain-oriented electrical steel sheet of the present embodiment, in a cross-sectional view of a plane parallel to the rolling direction and the sheet thickness direction, the average thickness of the intermediate layer in the central portion is more preferably 1.5 to 2 times the average thickness of the intermediate layer other than the deformed region. Here, the central portion refers to a central portion of a deformation region described later.
With this configuration, the adhesion of the insulating film can be maintained well even in the deformed region.
Typically, a plurality of deformed regions are formed substantially continuously (e.g., continuously except for the seam of the deformed regions) in the rolling direction. Therefore, a region between the nth deformed region counted in the rolling direction and, for example, the (N + 1) th deformed region (or the (N-1) th deformed region) adjacent to the nth deformed region in the rolling direction may be referred to as a region other than the deformed region.
The average thickness of the intermediate layer other than the deformed region can be measured by a Scanning Electron Microscope (SEM) or a Transmission Electron Microscope (TEM) by the method described below. The average thickness of the intermediate layer in the deformed region may be measured by the same method.
Specifically, the average thickness of the intermediate layer in the deformed region and the average thickness of the intermediate layer other than the deformed region can be measured by the method described below.
First, the test piece was cut so that the cutting direction was parallel to the plate thickness direction (specifically, the test piece was cut so that the cutting plane was parallel to the plate thickness direction and perpendicular to the rolling direction), and the cross-sectional structure of the cutting plane was observed by SEM at the magnification at which each layer (i.e., the base steel plate, the intermediate layer, and the insulating film) entered in the observation field. When observation is performed using a reflected electron composition image (comp image), it is possible to estimate what layer the cross-sectional structure is composed of.
For specifying each layer in the cross-sectional structure, a quantitative analysis of the chemical composition of each layer was performed by performing a line analysis along the plate thickness direction using SEM-EDS (Energy dispersive X-ray Spectroscopy).
The elements to be quantitatively analyzed were 5 elements of Fe, Cr, P, Si, and O. The "atomic%" described below is not an absolute value of atomic%, but is a relative value calculated based on the X-ray intensity corresponding to these 5 elements.
The relative values measured by SEM-EDS are specific values calculated by performing a line analysis using a scanning electron microscope (NB5000) manufactured by Hitachi High-Tech and an EDS analyzer (xflash (r)6|30) manufactured by Bruker AXS ltd, and inputting the results into EDS data software (ESPRIT1.9) manufactured by Bruker AXS ltd.
The relative value measured by TEM-EDS is a specific value calculated by performing a line Analysis using a transmission electron microscope (JEM-2100F) manufactured by japan electronics limited and an energy dispersive X-ray analyzer (jet-2300T) manufactured by japan electronics limited, and inputting the result into EDS data software (Analysis Station) manufactured by japan electronics limited. That is, the measurement by SEM-EDS and TEM-EDS is not limited to the examples shown below.
First, the base steel sheet, the intermediate layer, and the insulating film were specified as follows based on the observation results of the comp image and the quantitative analysis results of SEM EDS. That is, when there is a region where the Fe content removal measurement noise is 80 atomic% or more and the O content is less than 30 atomic%, and the line segment (thickness) on the scanning line of the line analysis corresponding to this region is 300nm or more, this region is determined as the base steel sheet, and the region excluding this base steel sheet is determined as the intermediate layer or the insulating film.
As a result of observation of the region other than the specific base steel sheet, a region having a P content of 5 atomic% or more and an O content of 30 atomic% or more was present except for the measurement noise, and a line segment (thickness) on a scanning line of a line analysis corresponding to the region was 300nm or more, it was judged that the region was an insulating film.
When a region as the insulating film is specified, a region satisfying the quantitative analysis result as a parent phase is determined as the insulating film without putting precipitates, inclusions, or the like contained in the film into a determination target. For example, when the presence of precipitates, inclusions, or the like on a scanning line of the on-line analysis is confirmed from a comp image or a line analysis result, the region is not put into an object, and is determined as a result of quantitative analysis of the parent phase. In addition, the precipitates or inclusions can be distinguished from the parent phase by comparison in a comp image, and can be distinguished from the parent phase by the amount of the constituent element present in the result of quantitative analysis.
If there is a region other than the specific base steel sheet and the insulating film and the line segment (thickness) on the scanning line of the line analysis corresponding to the region is 300nm or more, the region is determined as an intermediate layer. The intermediate layer may be defined as the average of the whole (for example, an arithmetic average of atomic% of each element measured at each measurement point on a scanning line) as long as the Si content satisfies 20 atomic% or more on average and the O content satisfies 30 atomic% or more on average. The quantitative analysis result of the intermediate layer does not include the analysis result of precipitates, inclusions, and the like contained in the intermediate layer, and is the quantitative analysis result of the matrix phase.
In the region determined as the insulating film, the region in which the total content of Fe, Cr, P, and O is 70 atomic% or more and the Si content is less than 10 atomic% is determined as the precipitate, except for the measurement noise.
As described later, the crystal structure of the precipitates can be specified by a pattern of electron beam diffraction.
In addition, the presence of M in conventional insulating films2P2O7But in the case of M2P2O7(M is at least one of Fe or Cr or both) can be distinguished by the pattern of electron beam diffraction specifying its crystal structure.
The observation field was changed, and the identity and thickness of each layer were measured at 5 or more points by the above-mentioned COMPO image observation and SEM-EDS quantitative analysis. An arithmetic average value was obtained from the thickness of each layer obtained at 5 or more points in total, excluding the maximum value and the minimum value, and the average value was defined as the thickness of each layer. However, the thickness of the oxide film as the intermediate layer was measured at a position where it can be determined that the oxide film is an external oxide region but not an internal oxide region while observing the morphology of the structure, and an average value was obtained. By this method, the thickness (average thickness) of the insulating film and the intermediate layer can be measured.
In addition, when there is a layer having a line segment (thickness) of less than 300nm on the scanning line of the line analysis in at least one place of the observation field of 5 or more, it is preferable to observe the layer in detail by TEM and measure the specification and thickness of the layer by TEM.
More specifically, a test piece including a layer to be observed in detail by TEM is cut so that a cutting direction is parallel to a plate thickness direction by FIB (Focused Ion Beam) processing (in detail, the test piece is cut so that a cut surface is parallel to the plate thickness direction and perpendicular to a rolling direction), and a cross-sectional structure of the cut surface is observed by STEM (Scanning-TEM) at a magnification at which the layer enters in an observation field (bright field image). When the layers do not enter the observation field of view, the cross-sectional structure is observed using a plurality of fields of view in succession.
In order to specify each layer in the cross-sectional structure, a line analysis was performed along the thickness direction using TEM-EDS, and quantitative analysis of the chemical composition of each layer was performed. The elements subjected to quantitative analysis were 5 elements of Fe, Cr, P, Si, and O.
Each layer was specified from the observation results of the bright field image in the TEM and the quantitative analysis results of the TEM-EDS, and the thickness of each layer was measured. The method for specifying each layer using TEM and the method for measuring the thickness of each layer may be the method using SEM described above.
In addition, when the thickness of each layer specified by TEM is 5nm or less, it is preferable to use TEM having a spherical aberration correction function from the viewpoint of spatial resolution. When the thickness of each layer is 5nm or less, the thickness of each layer can be determined by performing point analysis at intervals of, for example, 2nm or less in the thickness direction, measuring line segments (thicknesses) of each layer, and using the line segments as the thickness of each layer. For example, when a TEM having a spherical aberration correction function is used, EDS analysis can be performed with a spatial resolution of about 0.2 nm.
In the above-described method for specifying each layer, the base steel sheet is first specified over the entire region, the insulating coating in the remaining portion is then specified, the remaining portion is finally determined as the intermediate layer, and the precipitates are further specified.
(insulating film)
The insulating coating is prepared from phosphate and colloidal silicon dioxide (SiO)2) A vitreous insulating film formed by applying a solution as a main component to the surface of the intermediate layer and sintering the solution. Alternatively, a solution mainly containing alumina colloid and boric acid may be applied and sintered to form an insulating film.
The insulating film can impart a high surface tension to the base steel sheet. The insulating film constitutes, for example, the outermost surface of the grain-oriented electrical steel sheet.
The average thickness of the insulating film is preferably 0.1 to 10 μm. If the average thickness of the insulating film is less than 0.1 μm, the film adhesion of the insulating film may not be improved, and it may be difficult to impart a desired surface tension to the steel sheet. Therefore, the average thickness is preferably 0.1 μm or more, more preferably 0.5 μm or more on average.
If the average thickness of the insulating film exceeds 10 μm, cracks may be generated in the insulating film at the stage of forming the insulating film. Therefore, the average thickness is preferably 10 μm or less, more preferably 5 μm or less on average.
In consideration of recent environmental problems, the average Cr concentration in the insulating film is preferably limited to less than 0.10 atomic%, and more preferably limited to less than 0.05 atomic%, as a chemical component.
(deformation region)
The deformed region formed in the base steel sheet will be described with reference to fig. 3 and 4.
Fig. 3 is a schematic view showing a cross section of a plane parallel to the rolling direction and the plate thickness direction, and is a view including a deformed region D formed on the surface of the base steel plate 1. As shown in fig. 3, an intermediate layer 4 is disposed in contact with the base steel sheet 1, and an insulating film 3 is disposed in contact with the intermediate layer 4, thereby forming a deformation region D on the surface of the base steel sheet 1. In fig. 3, the intermediate layer 4 is represented by a line because the intermediate layer 4 has a smaller thickness than other layers.
Here, the center of the deformed region means the center between the ends of the deformed region in the rolling direction when viewed in cross section on a plane parallel to the rolling direction and the plate thickness direction, and for example, when the distance between the ends of the deformed region in the rolling direction is 40 μm, the center of the deformed region is located at a position 20 μm away from each end. In the cross-sectional view of fig. 3, the center c of the deformed region is indicated by a point located at an equal distance from the ends e and e' of the deformed region D.
In the example shown in fig. 3, the insulating film formed on the deformation region D of the base steel sheet is a region of the insulating film 3 sandwiched between the end e and the end e'.
The end e or the end e' of the deformed region D shown in fig. 3 can be determined by a CI (Confidential Index) value image of an EBSD (Electron Back Scatter Diffraction) image, for example. That is, in the region where the distortion is accumulated by irradiation of the electron beam, the lattice is distorted, and hence the CI value is different from that of the non-irradiated region. Here, for example, a CI value image of an EBSD of an area including both an irradiated area and an unirradiated area is acquired, an arithmetic average of an upper limit value and a lower limit value (excluding measurement noise) of a CI value in the image is set as a threshold, and the area in the image is divided into an area having a CI value equal to or greater than the threshold and an area having a CI value smaller than the threshold. Further, one of the regions is defined as a deformed region (irradiated region), and the other region is defined as a region other than the deformed region (non-irradiated region). Thereby, the deformed region can be specified.
Fig. 4 is a schematic view showing a cross section of a plane parallel to the rolling direction and the plate thickness direction, and is an enlarged view of a range a surrounded by a broken line in fig. 3. Fig. 4 shows a range including the center portion C of the deformation region D.
The central portion of the deformed region is a region including the center of the deformed region and having a width of 10 μm in the rolling direction. In fig. 4, the center portion C of the deformed region D is shown surrounded by a straight line m and a straight line m'. The lines m and m' are lines perpendicular to the rolling direction of the base steel sheet 1 and parallel to each other, and have a 10 μm interval. In the example of fig. 4, the distances from the straight line m and the straight line m' to the center c of the deformed region D are the same.
Further, in the rolling direction, the position of the center of the deformed region and the center of the central portion of the deformed region more preferably coincide.
The width of the deformed region D, which is the distance between the end e and the end e', is preferably 10 μm or more, more preferably 20 μm or more. The width of the deformed region D is preferably 500 μm or less, more preferably 100 μm or less.
In the grain-oriented electrical steel sheet of the present embodiment, it is more preferable that M be present in the insulating coating in the central portion of the deformed region2P4O13. M represents at least one or both of Fe and Cr.
In the example shown in fig. 4, M is present in the insulating film 3 in the central portion C of the deformation region D2P4O13The precipitate of (2). In fig. 4, the precipitates are referred to as regions 5. In addition, a region 6 containing precipitates of an amorphous phosphorus oxide exists around the region 5 in fig. 4. In the insulating film 3, the regions excluding the regions 5 and 6 include a matrix phase 7 or pores 8 of the insulating film.
Furthermore, region 5 may consist of only M2P4O13May further contain M2P4O13And other precipitates. In addition, the region 6 may be composed of only amorphous phosphorus oxideThe precipitate composition of (3) may be a region containing precipitates of the amorphous phosphorus oxide and other precipitates.
M2P4O13Is a phosphorus oxide, e.g. Fe2P4O13Or Cr2P4O13、(Fe,Cr)2P4O13。
The region 6 may be formed near the surface of the insulating film 3.
The matrix phase 7 of the insulating film contains P, Si, and O as a composition.
M2P4O13The precipitates of (a) or the precipitates of the amorphous phosphorus oxide can be identified by a method of analyzing an electron beam diffraction pattern.
This identification can be performed using PDF (Powder Diffraction File) of ICDD (International Centre for Diffraction Data). Specifically, when the precipitate is M2P4O13When, PDF is presented: 01-084-1956 diffraction Pattern, the precipitate was M present in the conventional insulating coating2P2O7When, PDF is presented: 00-048 and 0598. In addition, when the precipitates are amorphous phosphorus oxide, the diffraction pattern becomes a Halo (Halo) pattern.
In the grain-oriented electrical steel sheet of the present embodiment, M is present in the insulating coating at the center of the deformation region2P4O13When the deformation region is formed at an energy density that provides a good iron loss reduction effect, good adhesion of the insulating film can be ensured.
In the grain-oriented electrical steel sheet of the present embodiment, as shown in fig. 5, when the total length of the observation field in the direction perpendicular to the sheet thickness direction is L in the cross-sectional view of the deformed region on the plane parallel to the rolling direction and the sheet thickness directionzLength L of the hole in the direction perpendicular to the plate thickness directiond(L in the example of FIG. 5)1～L4) Is taken as sigma LdThe line segment fraction X of the pore region where pores exist is determined by the following formula (1)When defined, the line segment fraction X is more preferably 20% or less.
X＝(ΣLd/Lz) X 100 (formula 1)
With this configuration, peeling of the insulating film from the pores is suppressed, and the adhesion of the insulating film is improved.
Length L of the poredThe method can be specified as follows. The insulating film specified by the above method was observed with TEM (bright field image). In the bright field image, the white area becomes a void. Whether or not the white region is a void can be clearly distinguished by the TEM-EDS. Visual field of observation (full Length L)z) In the above, the region that is the void in the insulating film and the region that is not the void are binarized, and the length L of the void in the direction perpendicular to the plate thickness direction can be obtained by image analysisd。
Here, in the example of fig. 5, the length L of the aperture 8dSum of ∑ LdIs Σ Ld＝L1+L2+L3+L4. When the apertures 8 are overlapped in the plate thickness direction, as shown in fig. 5, the length L from the overlapped aperturesdThe length of the overlapping portion is subtracted and the value is taken as the length of the aperture. In FIG. 5, the length of the overlapping 2 apertures 8 is L minus the length of the overlapping length when viewed in the plate thickness direction4。
The line segment fraction X is more preferably 10% or less from the viewpoint of improving the adhesion of the insulating film. The lower limit of the line segment fraction X is not particularly limited, and may be 0%.
The binarization of the image for image analysis may be performed by manually filling up the gaps in the tissue photograph based on the result of the pore discrimination.
The observation field of view may be a central portion of the deformed region. That is, the entire length L of the observation field can be setzThe thickness was set to 10 μm.
The line segment fraction X of voids was measured at 3 points with an interval of 50mm or more in the direction perpendicular to the rolling direction and the thickness direction of the base steel sheet for the same deformed region, and the arithmetic mean of these line segment fractions was defined as the line segment fraction X.
In the grain-oriented electrical steel sheet of the present embodiment, the deformed region D is more preferably provided continuously or discontinuously when viewed in a direction perpendicular to the sheet surface of the base steel sheet 1. The continuously provided deformed region D means that the deformed region D is formed to be 5mm or more in a direction intersecting the rolling direction of the base steel plate 1. The discontinuously provided deformed region D is a deformed region D formed in a dotted shape or an intermittent linear shape of 5mm or less in a direction intersecting the rolling direction of the base steel sheet 1.
With this structure, the effect of refining magnetic domains can be stably obtained.
In the grain-oriented electrical steel sheet of the present embodiment, M in the insulating film in the center portion is M in the cross-sectional view of the plane parallel to the rolling direction and the sheet thickness direction2P4O13The proportion is more preferably 10% to 60% in terms of area ratio.
The area ratio is preferably 20% or more, more preferably 30% or more. The area ratio is preferably 50% or less, more preferably 40% or less. With this configuration, the effect of improving the adhesion of the insulating film is obtained.
M in insulating coating of center part2P4O13The area ratio of (A) can be determined by specifying precipitates by the above-mentioned method and analyzing M by an electron beam diffraction pattern2P4O13The precipitates of (a) were identified and calculated. M in insulating coating of center part2P4O13Is M in the same section2P4O13The ratio of the total cross-sectional area of (a) to the total cross-sectional area of the insulating film in the central portion including precipitates or pores. These cross-sectional areas may be calculated by image analysis or may be calculated from a photograph of the cross-section.
In the grain-oriented electrical steel sheet of the present embodiment, the area ratio of the amorphous phosphorus oxide region in the insulating film in the central portion is more preferably 1% to 60% in a cross-sectional view of a plane parallel to the rolling direction and the sheet thickness direction.
The area ratio of the amorphous phosphorus oxide region is 1% or more, and local stress in the insulating film is relaxed. The area ratio of the amorphous phosphorus oxide region is 60% or less, and an effect of not lowering the tension of the insulating film is obtained.
The area ratio of the amorphous phosphorus oxide region is more preferably 5% or more, and the area ratio of the amorphous phosphorus oxide region is more preferably 40% or less. The area ratio of the amorphous phosphorus oxide region in the insulating film in the central portion can be determined by the ratio of M in the insulating film in the central portion2P4O13The area ratios of (A) and (B) are measured by the same method.
In the cross-sectional views, the deformed region D in the base steel sheet 1 of the grain-oriented electrical steel sheet of the present embodiment can be identified by using the ci (structural index) value image of ebsd (electron Back Scatter) as described above.
The grain-oriented electrical steel sheet of the present embodiment is not particularly limited in the composition of the base steel sheet. However, since the grain-oriented electrical steel sheet is manufactured through various processes, the component compositions of the billet (slab) and the base steel sheet are preferably present when the grain-oriented electrical steel sheet according to the present embodiment is manufactured. The following describes the composition of these components.
Hereinafter, the% relating to the composition of the raw material slab and the base steel sheet means mass% with respect to the total mass of the raw material slab or the base steel sheet.
(composition of base Steel plate)
The base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment contains, for example, Si: 0.8-7.0%, with the limitation of C: 0.005% or less, N: 0.005% or less, total amount of S and Se: 0.005% or less and acid-soluble Al: less than 0.005%, and the balance of Fe and impurities.
Si：0.8％～7.0％
Si (silicon) increases the electrical resistance of grain-oriented electrical steel sheets and reduces the iron loss. The lower limit of the Si content is preferably 0.8% or more, more preferably 2.0% or more. On the other hand, if the Si content exceeds 7.0%, the saturation magnetic flux density of the base steel sheet decreases, and therefore, there is a possibility that the size reduction of the iron core becomes difficult. Therefore, the preferable upper limit of the Si content is 7.0% or less.
C: less than 0.005%
C (carbon) forms a compound in the base steel sheet and deteriorates the iron loss, and therefore, it is preferable that the amount of C is as small as possible. The C content is preferably limited to 0.005% or less. The upper limit of the C content is preferably 0.004% or less, more preferably 0.003% or less. The lower limit is preferably 0% as the amount of C is smaller, but when C is reduced to less than 0.0001%, the production cost is greatly increased, and therefore 0.0001% is a substantial lower limit in production.
N: less than 0.005%
N (nitrogen) forms a compound in the base steel sheet and deteriorates the iron loss, and therefore, the smaller the amount of N (nitrogen) is, the better. The N content is preferably limited to 0.005% or less. The upper limit of the N content is preferably 0.004% or less, more preferably 0.003% or less. The lower the amount of N is, the more preferable, the lower limit may be 0%.
Total amount of S and Se: less than 0.005%
S (sulfur) and Se (selenium) form compounds in the base steel sheet and deteriorate the iron loss, and therefore, the smaller the amount of S (sulfur) and Se (selenium) is, the better. The total of one or both of S and Se is preferably limited to 0.005% or less. The total amount of S and Se is preferably 0.004% or less, more preferably 0.003% or less. The lower the content of S or Se is, the more preferable the lower limit is 0% each.
Acid-soluble Al: less than 0.005%
Since acid-soluble Al (acid-soluble aluminum) forms a compound in the base steel sheet and deteriorates the iron loss, it is preferable that the amount of the acid-soluble Al is as small as possible. The acid-soluble Al content is preferably 0.005% or less. The acid-soluble Al is preferably 0.004% or less, more preferably 0.003% or less. The lower limit is preferably 0% as the amount of acid-soluble Al is smaller.
The remainder of the composition of the base steel sheet contains Fe and impurities. The term "impurities" refers to substances mixed in from ores and waste materials as raw materials, production environments, and the like in the industrial production of steel.
The base steel sheet of the grain-oriented electrical steel sheet according to the present embodiment may contain, as optional elements, at least 1 selected from Mn (manganese), Bi (bismuth), B (boron), Ti (titanium), Nb (niobium), V (vanadium), Sn (tin), Sb (antimony), Cr (chromium), Cu (copper), P (phosphorus), Ni (nickel), and Mo (molybdenum), for example, in place of a part of Fe as the remainder within a range not to impair the characteristics.
The content of the above-mentioned optional elements may be, for example, as follows. The lower limit of the selected element is not particularly limited, and the lower limit may be 0%. Even if these optional elements are contained as impurities, the effects of the grain-oriented electrical steel sheet of the present embodiment are not impaired.
Mn：0％～1.00％、
Bi：0％～0.010％、
B：0％～0.008％、
Ti：0％～0.015％、
Nb：0％～0.20％、
V：0％～0.15％、
Sn：0％～0.30％、
Sb：0％～0.30％、
Cr：0％～0.30％、
Cu：0％～0.40％、
P：0％～0.50％、
Ni: 0% -1.00% and Mo: 0 to 0.10 percent.
The chemical components of the base steel sheet may be measured by a general analysis method. For example, the steel composition may be measured by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Further, C and S may be measured by a combustion-infrared absorption method, N may be measured by an inert gas melting-heat conduction method, and O may be measured by an inert gas melting-non-dispersive infrared absorption method.
The base steel sheet of the grain-oriented electrical steel sheet of the present embodiment preferably has a grain texture developed in {110} <001> orientation. The {110} <001> orientation means a crystal orientation (gaussian orientation) in which the {110} plane is aligned parallel to the steel sheet surface and the <100> axis is aligned in the rolling direction. In grain-oriented electrical steel sheets, it is preferable to improve the magnetic properties by controlling the crystal orientation of the base steel sheet to be gaussian.
The texture of the base steel sheet may be measured by a general analysis method. For example, the measurement may be performed by an X-ray diffraction method (Laue method). The laue method is a method of irradiating a steel sheet with X-ray electron beams perpendicularly to analyze transmitted or reflected diffraction spots. By analyzing the diffraction spots, the crystal orientation of the position irradiated with the X-ray electron beam can be identified. When the irradiation position is changed and diffraction spots are analyzed at a plurality of positions, the crystal orientation distribution at each irradiation position can be measured. The laue method is a method suitable for measuring the crystal orientation of a metal structure having coarse grains.
Further, each layer of the grain-oriented electrical steel sheet of the present embodiment is observed and measured as follows.
The test piece was cut from the grain-oriented electrical steel sheet, and the film structure of the test piece was observed by a scanning electron microscope or a transmission electron microscope.
Specifically, first, the test piece is sheared so that the shearing direction is parallel to the plate thickness direction (specifically, the test piece is sheared so that the cut surface is parallel to the plate thickness direction and perpendicular to the rolling direction), and the cross-sectional structure of the cut surface is observed by SEM at a magnification of entering each layer in the observation field. By observing with a reflected electron composition image (comp image), it can be analogized by what layer the cross-sectional structure is composed of.
In order to specify each layer in the cross-sectional structure, quantitative analysis of the chemical composition of each layer was performed by performing line analysis along the plate thickness direction using SEM-EDS (Energy Dispersive X-ray Spectroscopy).
The elements to be quantitatively analyzed were 5 elements of Fe, Cr, P, Si, and O. The "atomic%" described below is not an absolute value of atomic%, but is a relative value calculated based on the X-ray intensity corresponding to these 5 elements. Specific numerical values when the relative values are calculated using the above-described device and the like are shown below.
First, the base steel sheet, the intermediate layer, and the insulating film were specified as follows based on the observation results of the comp image and the quantitative analysis results of SEM EDS. That is, when there is a region where the Fe content removal measurement noise is 80 atomic% or more and the O content is less than 30 atomic%, and the line segment (thickness) on the scanning line of the line analysis corresponding to this region is 300nm or more, this region is determined as the base steel sheet, and the region excluding this base steel sheet is determined as the intermediate layer or the insulating film.
As a result of observing the region other than the specific base steel sheet, it was judged that the region was an insulating film when the region had a P content of 5 atomic% or more and an O content of 30 atomic% or more, and a line segment (thickness) on a scanning line of a line analysis corresponding to the region was 300nm or more, excluding measurement noise.
When a region as the insulating film is specified, a region satisfying the quantitative analysis result as a parent phase is determined as the insulating film without putting precipitates, inclusions, or the like contained in the film into a determination target. For example, when the presence of precipitates, inclusions, or the like on a scanning line of the on-line analysis is confirmed from a comp image or a line analysis result, the region is not put into an object, and is determined as a result of quantitative analysis of the parent phase. In addition, the precipitates or inclusions can be distinguished from the parent phase by comparison in a comp image, and can be distinguished from the parent phase by the amount of the constituent element present in the result of quantitative analysis.
If there is a region other than the specific base steel sheet and the insulating film and the line segment (thickness) on the scanning line of the line analysis corresponding to the region is 300nm or more, the region is determined as an intermediate layer. The intermediate layer may be defined as the average of the whole (for example, an arithmetic average of atomic% of each element measured at each measurement point on a scanning line) as long as the Si content satisfies 20 atomic% or more on average and the O content satisfies 30 atomic% or more on average. The quantitative analysis result of the intermediate layer does not include the analysis result of precipitates, inclusions, and the like contained in the intermediate layer, and is the quantitative analysis result of the matrix phase.
In the region determined as the insulating film, the region in which the total content of Fe, Cr, P, and O is 70 atomic% or more and the Si content is less than 10 atomic% is determined as the precipitate, except for the measurement noise.
As described later, the crystal structure of the precipitates can be specified by a pattern of electron beam diffraction.
In addition, the presence of M in conventional insulating films2P2O7But in the case of M2P2O7(M is at least one of Fe or Cr or both) can be distinguished by the pattern of electron beam diffraction specifying its crystal structure.
The observation field was changed, and the identity and thickness of each layer were measured at 5 or more points by the above-mentioned COMPO image observation and SEM-EDS quantitative analysis. An arithmetic average value was obtained from the thickness of each layer obtained at 5 or more points in total, excluding the maximum value and the minimum value, and the average value was defined as the thickness of each layer. However, the thickness of the oxide film as the intermediate layer was measured at a position where it can be determined that the oxide film is an external oxide region but not an internal oxide region while observing the morphology of the structure, and an average value was obtained.
In the deformation region, the average thickness of the intermediate layer and the average thickness of the insulating film can be calculated by the same method.
In addition, when there is a layer having a line segment (thickness) of less than 300nm on the scanning line of the line analysis in at least one place of the observation field of 5 or more, it is preferable to observe the layer in detail by TEM and measure the specification and thickness of the layer by TEM.
More specifically, a test piece including a layer to be observed in detail by TEM is sheared so that the shearing direction is parallel to the plate thickness direction by fib (focused Ion beam) (in detail, the test piece is sheared so that the cut surface is parallel to the plate thickness direction and perpendicular to the rolling direction), and the cross-sectional structure of the cut surface is observed by STEM (Scanning-TEM) at a magnification at which the layer enters the observation field (bright field image). When the layers do not enter the observation field of view, the cross-sectional structure is observed using a plurality of fields of view in succession.
In order to specify each layer in the cross-sectional structure, a line analysis was performed along the thickness direction using TEM-EDS, and quantitative analysis of the chemical composition of each layer was performed. The elements subjected to quantitative analysis were 5 elements of Fe, Cr, P, Si, and O.
Each layer was specified from the observation results of the bright field image in the TEM and the quantitative analysis results of the TEM-EDS, and the thickness of each layer was measured. The method for specifying each layer using TEM and the method for measuring the thickness of each layer may be the method using SEM described above.
Specifically, a region where the Fe content removal measurement noise is 80 atomic% or more and the O content is less than 30 atomic% is determined as the base steel sheet, and a region excluding the base steel sheet is determined as the intermediate layer and the insulating film.
In the region other than the specific base steel sheet, a region having a P content of 5 atomic% or more and an O content of 30 atomic% or more excluding the measurement noise is determined as the insulating film. In the case of determining the region as the insulating film, a region satisfying the quantitative analysis result as a parent phase is determined as the insulating film without putting precipitates, inclusions, or the like contained in the insulating film into a determination target.
The region excluding the specific base steel sheet and the insulating film is determined as an intermediate layer. The average of the intermediate layer as a whole may be such that the Si content satisfies 20 atomic% or more on average and the O content satisfies 30 atomic% or more on average. The quantitative analysis result of the intermediate layer does not include the analysis result of precipitates, inclusions, and the like contained in the intermediate layer, and is the quantitative analysis result of the matrix phase.
In the region determined as the insulating film, the region in which the total content of Fe, Cr, P, and O is 70 atomic% or more and the Si content is less than 10 atomic% is determined as the precipitate, except for the measurement noise. As described above, the precipitates can be specified in the crystal structure by the pattern of diffraction by the electron beam.
The line segment (thickness) of the specific intermediate layer and insulating film was measured on the scanning line of the line analysis. When the thickness of each layer is 5nm or less, a TEM having a spherical aberration correction function is preferably used from the viewpoint of spatial resolution. When the thickness of each layer is 5nm or less, the thickness of each layer can be determined by performing point analysis at intervals of, for example, 2nm or less in the thickness direction, measuring line segments (thicknesses) of each layer, and using the line segments as the thickness of each layer. For example, when a TEM having a spherical aberration correction function is used, EDS analysis can be performed with a spatial resolution of about 0.2 nm.
Observation and measurement by the TEM were carried out at 5 or more positions while changing the observation field, and an arithmetic average value was obtained from the values excluding the maximum value and the minimum value among the measurement results obtained at 5 or more positions in total, and this average value was used as the average thickness of the layer. In the deformation region, the average thickness of the intermediate layer and the average thickness of the insulating film may be calculated by the same method.
In the grain-oriented electrical steel sheet of the above embodiment, since the intermediate layer is present in contact with the base steel sheet and the insulating film is present in contact with the intermediate layer, when each layer is specified according to the above criteria, the base steel sheet, the intermediate layer, and the layer other than the insulating film are absent. But also the above-mentioned M2P4O13The region (b) or the amorphous phosphorus oxide region may be in the form of a layer.
The contents of Fe, P, Si, O, Cr, and the like contained in the base steel sheet, the intermediate layer, and the insulating film are determination criteria for specifying the base steel sheet, the intermediate layer, and the insulating film and determining the thicknesses thereof.
In addition, when the coating adhesion of the insulating coating of the grain-oriented electrical steel sheet of the above embodiment was measured, a bending adhesion test was performed to evaluate the film adhesion. Specifically, a flat test piece of 80mm × 80mm was rolled into a round bar of 20mm in diameter, and then spread out flat. Next, the area of the insulating film that was not peeled from the electrical steel sheet was measured, and the area that was not peeled was divided by the area of the steel sheet, and the obtained value was defined as the film remaining area ratio (%), and the film adhesion of the insulating film was evaluated. For example, a transparent film with 1mm square marks may be placed on a test piece, and the area of the insulation film that has not been peeled off may be measured and calculated.
Iron loss (W) of grain-oriented electrical steel sheet17/50) Measured under the conditions that the AC frequency was 50 Hz and the excitation magnetic flux density was 1.7 Tesla.
Examples
Next, the effects of one aspect of the present invention will be described in more detail with reference to examples, but the conditions in the examples are only one example of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to this example of conditions.
In the present invention, various conditions can be adopted as long as the object of the present invention is achieved without departing from the gist of the present invention.
(Experimental example 1)
The slabs of the materials having the compositions shown in Table 1 were hot-rolled after being soaked at 1150 ℃ for 60 minutes to obtain hot-rolled steel sheets having a thickness of 2.3 mm. Subsequently, the hot-rolled steel sheet was held at 1120 ℃ for 200 seconds, immediately cooled, held at 900 ℃ for 120 seconds, and then subjected to rapid-cooling hot-rolled sheet annealing. The hot-rolled annealed sheet after annealing was subjected to acid washing and then subjected to cold rolling to obtain a cold-rolled steel sheet having a final thickness of 0.23 mm.
TABLE 1
Figure BDA0003159535690000281
The cold-rolled steel sheet (hereinafter referred to as "steel sheet") was subjected to heating in the presence of hydrogen: the nitrogen content is 75%: decarburization annealing was performed at 850 ℃ for 180 seconds in an atmosphere of 25%. The decarburized and annealed steel sheet was subjected to nitriding annealing at 750 ℃ for 30 seconds in a mixed atmosphere of hydrogen, nitrogen and ammonia, and the nitrogen content of the steel sheet was adjusted to 230 ppm.
After the steel sheet after nitriding annealing is coated with an annealing separating agent containing alumina as a main component, the steel sheet is heated to 1200 ℃ at a temperature increase rate of 10 ℃/hr in a mixed atmosphere of hydrogen and nitrogen, and final annealing is performed. Subsequently, the steel sheet was subjected to purification annealing at 1200 ℃ for 20 hours in a hydrogen atmosphere. Subsequently, the steel sheet is naturally cooled to produce a base steel sheet having a smooth surface.
For the produced base steel sheet, an intermediate layer was formed under the conditions shown in Table 2
A solution mainly containing phosphate and colloidal silica was applied to the surface of the base steel sheet having the intermediate layer formed thereon under the conditions shown in table 2, and an insulating film was formed under the conditions shown in table 2.
Figure BDA0003159535690000291
Next, under the conditions shown in table 3, an electron beam was irradiated to form a deformed region, thereby obtaining grain-oriented electrical steel sheets of the respective experimental examples. In table 3, "the temperature of the central portion of the deformed region" means the temperature of the central portion of the deformed region in the rolling direction and the extending direction of the deformed region of the base steel sheet.
TABLE 3
Figure BDA0003159535690000301
According to the observation and measurement method of the above embodiment, test pieces are cut from the directional electromagnetic steel sheets, the film structure of each test piece is observed by a Scanning Electron Microscope (SEM) or a Transmission Electron Microscope (TEM), and the specification of the deformation region and the central portion of the deformation region, the thickness of the intermediate layer, the thickness of the insulating film, and the like are performed. In addition, the precipitates were specified. The specific method is as described above.
Table 4 shows the presence or absence of M in the insulating coating film in the deformed region2P4O13The result of (1). As shown in table 4, in the grain-oriented electrical steel sheet produced by the production method according to the present embodiment, M is present in the insulating coating film on the deformed region2P4O13。
TABLE 4
Figure BDA0003159535690000311
Next, a test piece of 80mm × 80mm was cut out from the grain-oriented electrical steel sheet on which the insulating coating was formed, and the test piece was rolled into a round bar having a diameter of 20mm, and then spread flat. Then, the area of the insulating film that was not peeled off from the electrical steel sheet was measured, and the remaining area ratio (%) of the film was calculated. The results are shown in table 4 as the adhesion of the coating. The adhesion of the insulating film was evaluated in two stages. "good" means that the residual area ratio of the coating film is 90% or more. "poor" means that the residual area ratio of the coating film is less than 90%.
As is clear from table 4, the grain-oriented electrical steel sheet produced by the production method of the present invention has good adhesion.
In addition, the iron loss of the grain-oriented electrical steel sheets of the respective experimental examples was measured. The results are shown in Table 4.
As shown in table 4, it is understood that the grain-oriented electrical steel sheet produced by the production method of the present invention has a reduced iron loss.
Industrial applicability
According to the present invention, there can be provided a method for producing a grain-oriented electrical steel sheet, in which a forsterite film is not formed and a deformed region is formed on a base steel sheet, and a good adhesion of the insulating film can be ensured, thereby obtaining a good iron loss reduction effect. Therefore, the industrial applicability is high.
Description of the symbols
1 base steel sheet
2 forsterite film
3 insulating coating
4 intermediate layer
5 comprises M2P4O13Region of precipitates of (2)
6 region containing precipitates of amorphous phosphorus oxide
7 parent phase of insulating coating
8 pores.

Claims (5)

1. A method for manufacturing a grain-oriented electrical steel sheet, comprising the steps of:
a deformation region forming step of irradiating an electron beam to a grain-oriented electrical steel sheet having a base steel sheet, an intermediate layer disposed in contact with the base steel sheet, and an insulating film disposed in contact with the intermediate layer, and forming a deformation region extending in a direction intersecting a rolling direction of the base steel sheet on a surface of the base steel sheet,
in the deformed region forming step, the temperature of the center portion of the deformed region in the rolling direction of the base steel sheet and the extending direction of the deformed region is heated to 800 to 2000 ℃.
2. The method of manufacturing a grain-oriented electrical steel sheet according to claim 1, wherein in the deformed region forming step, a central portion of the deformed region in a rolling direction of the base steel sheet and an extending direction of the deformed region is heated to 800 ℃ to 1500 ℃.
3. The method of manufacturing a grain-oriented electrical steel sheet according to claim 1 or 2, wherein in the deformed region forming step, irradiation conditions of electron beams are set to
Acceleration voltage: 50kV to 350kV,
Beam current: 0.3 mA-50 mA,
Electron beam irradiation diameter: 10-500 mu m,
Irradiation interval: 3 mm-20 mm,
Scanning speed: 5 m/s to 80 m/s.
4. The method of manufacturing a grain-oriented electrical steel sheet according to any one of claims 1 to 3, further comprising an intermediate layer forming step of forming the intermediate layer on the base steel sheet, wherein in the intermediate layer forming step, the annealing temperature is adjusted to be: 500-1500 ℃, holding time: 10-600 seconds, dew point: heat-treating the base steel sheet under annealing conditions of-20 to 5 ℃ to form an intermediate layer.
5. The method of producing a grain-oriented electrical steel sheet according to any one of claims 1 to 4, further comprising an insulating film forming step of forming the insulating film on the base steel sheet on which the intermediate layer is formed,
in the insulating film forming step, the coating amount is 2g/m2～10g/m2Applying an insulating film-forming solution on the surface of the base steel sheet,
the base steel sheet coated with the insulating film-forming solution is left for 3 to 300 seconds,
at a pH of oxidation containing hydrogen and nitrogen2O/PH2Heating the base steel sheet coated with the insulating film-forming solution at a temperature increase rate of 5 ℃/second to 30 ℃ second in an atmosphere gas adjusted to 0.001 to 0.3,
at a pH of oxidation containing hydrogen and nitrogen2O/PH2Soaking the heated base steel sheet in an atmosphere gas adjusted to 0.001 to 0.3 at a temperature of 300 to 950 ℃ for 10 to 300 seconds,
at a pH of oxidation containing hydrogen and nitrogen2O/PH2And cooling the base material steel plate, which is soaked, to 500 ℃ at a cooling rate of 5 ℃/second to 50 ℃ second in an atmosphere gas controlled to be 0.001 to 0.05 ℃.
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